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    <title>Document</title>
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<body>
    <div>盒子尺寸设置模型</div>
    <style>
        div{
            width: 200px;
            height: 130px;
            background-color: #aa6;
            border: 1px solid red;
            background-clip: content-box;
            padding: 10px 20px 30px  ; /*先观察整体，然后删除40px，再观察，再删除30px....*/
            }
    </style>
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